1. Field of the Invention
The present invention relates to cell broadcasting in a communication system, and more particularly, to a method for the cell broadcasting of short messages in a 3GPP communication system, in which a new schedule message scheme is adopted.
2. Discussion of the Related Art
Short message service (SMS) is a service provided by a network for the transmission of alphanumeric messages to a mobile station, i.e., a user equipment (UE), which may “receive” a short message even in an idle state. The short message may be initiated by a cellular telephone, an information service, or the network itself and may include such information as that for email notification, voicemail notification, cellular messaging teleservice, or cellular paging teleservice.
Standards for SMS technology include IS-637 for a CDMA environment and IS-95 and J-STD-008 for a radio environment. In the CDMA environment, a service center provides short messages, which are received by a base station from a core network and are transmitted from the base station to a mobile station through a control channel, i.e., a paging channel. In the radio environment, a global system for mobile communications, known as the GSM system, supports a cell broadcasting of short messages, whereby SMS cell broadcasting (SMSCB) messages are broadcast over at least one cell from a public land mobile network to one or more mobile stations.
Referring to FIG. 1, a 3GPP communication system consists of a UE system, a network (UTRAN) system, and a core system (not shown). The UE and UTRAN systems utilize bidirectional channels, i.e., an uplink and a downlink, and each system includes a higher layer, a radio resource control (RRC) layer corresponding to layer 3, a radio link control (RLC) layer and a media access control (MAC) layer corresponding to layer 2, and a physical (PHY) layer corresponding to layer 1.
The physical layer provides a plurality of transmission channel types to the MAC layer, which in turn provides a plurality of logical channel types to the RLC layer. The transmission channels are either common channels or dedicated channels depending on the mode of transmission on a radio link, and the logical channels are either control channels or traffic channels depending on whether the data transmission service provided by the MAC layer to the RLC layer is transmitting control data or user data. In addition, the physical layer performs the encoding/decoding and multiplexing/demultiplexing of transmission channels and the modulation/demodulation and spreading/despreading of physical channels, performs chip, bit, slot & frame synchronization, controls transmit power and transmission rate, and performs frequency processing and error detection and correction.
The RLC layer receives from the higher layer a message corresponding to a service selected by a user, and the RRC layer controls a logical connection of the lower layers, i.e., the RLC, MAC, and physical layers, which provide the services selected at the higher layer. To this end, the RRC layer is respectively connected to each of the lower layers by a service access point (not shown in FIG. 1) through which primitives are transmitted and received for controlling the RRC layer. The RRC layer thus confirms, maintains, and releases the logical connections and assigns, reconstructs, and releases radio resources for each connection.
Upon receiving a service message from the higher layer, the RLC layer controls the radio link with a corresponding system, i.e., the UE or UTRAN system. In doing so, the RLC layer divides (segments) and reconstructs the received service message, compresses the RLC header, and performs concatenation, padding, error correction, flow control, and transmission of capsulated data units, i.e., one or more frames. The MAC layer receives the capsulated data units from the RLC layer and, based on the compressed header, constructs MAC data units.
FIGS. 2 and 3 respectively show message schemes according to GSM standards, each for the cell broadcasting of the short messages, where an SMSCB message is diagrammed in FIG. 2 and a schedule message is diagrammed in FIG. 3. The SMSCB message is comprised of 88 octets, each field of the message being comprised of one or more octets, to include the message content preceded by a serial number field, a message identifier field, a data coding scheme field, and a page parameter field designating a total number of pages. The schedule message is similarly comprised of octets and includes fields for type, start slot number, end slot number, new SMSCB message bitmap, new SMSCB message description, other message descriptions.
Cell broadcasting of an SMS message as above is performed in the GSM system according to one of two modes, i.e., a discontinuous reception (DRX) mode or a non-discontinuous reception (non-DRX) mode, according to the type of short message being transmitted from the higher layer. In the DRX mode, the UE uses the schedule message to read the SMSCB message, but only when a desired SMSCB message is renewed, and ignores all other message data. In the non-DRX mode, the UE reads all frames, i.e., all data units transmitted on the radio link, to read any desired SMSCB message without the information of a schedule message, by classifying each SMSCB message as desired or undesired based on their respective headers.
The SMSCB message and schedule message as above are adapted to the GSM system, where no message may exceed 88 octets, where the length of a SMSCB message may not exceed fifteen pages, and where each message must be accompanied by a header for each page. Further adaptation, however, is needed to apply the short message service of the CDMA environment or the SMS cell broadcasting of the GSM environment to a third-generation mobile communication (3GPP) system where macro message transmission is expected and where global roaming service is desired. Particularly, a suitable technical specification for SMS cell broadcasting is required for the 3GPP system, which is based on the core network of the GSM system and radio access technology.